An extractable nuclear antigen (ENA) panel detects the presence of one or more autoantibodies in the blood that react with proteins in the cell nucleus. These proteins are known as “extractable” because they can be removed from cell nuclei using saline. Autoantibodies are produced when a person’s immune system mistakenly targets and attacks the body’s own tissues. This attack can cause inflammation, tissue damage, and other signs and symptoms that are associated with an autoimmune disorder. Certain autoimmune disorders are characteristically associated with the presence of one or more anti-ENA antibodies. This association can be used to help diagnose an autoimmune disorder and to distinguish between disorders. Sample: Blood (serum) Reference: Negative Frequency: Twice a week